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Gear Inches Calculator — Compare Gears Across Wheel Sizes
Convert gear ratios to gear inches for cross-bike comparison.
How We Calculate This
Gear Inches Formula
Gear Inches = (Chainring / Sprocket) x Wheel Diameter (inches)
Wheel diameter in inches is derived from wheel circumference: Diameter = Circumference / pi / 25.4
Frequently Asked Questions
Gear inches is an older but still useful way to compare gears. It represents the effective wheel diameter of an equivalent directly-driven bicycle (like a penny-farthing).
Two bikes with different wheel sizes but the same gear inches travel the same distance per pedal revolution, so gear inches let you compare gearing directly across 700c, 650b, 26-inch and other wheels. Gear ratio alone cannot do this, because the same ratio on a smaller wheel covers less ground per pedal stroke.
Road bikes: 30-120 gear inches. Mountain bikes: 20-100. A comfortable cruising gear is about 65-75 gear inches.
Related Calculators
Gear Ratio Calculator
Calculate gear ratios from chainring and sprocket tooth counts.
Hub Gear Calculator
Calculate effective gear ratios for internal hub gear systems.
Gear Inch Calculator
Calculate gear inches, development in metres and speed at 80, 90 and 100 rpm for any chainring, cog, wheel size and tyre width combination.
Development Calculator
Calculate distance travelled per pedal revolution for any gear.
Cassette Calculator
Analyse cassette tooth counts and gear jumps between sprockets.
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Last updated: June 2026
All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.